Tag editor + Drag scroll button fix + Help ToC Chrome fix

* Added a tag editor for text inputs meant for tags.
* Made image drag scrolling only respond to the primary (left) click.
* Fixed the help page table of contents so that only the help tab gets scrolled when clicking a link in Chrome.
* Tweaked the styles some more. Overall, the rules have been made more specific to make them more resistant to Danbooru style changes. Rounded corners have also been added to the buttons and tabs.